Hello Everyone
I have a question regarding critical speed range,
We know when the turbine shaft passes through its critical range of speed its vibration values increases. Will turbine trip on vibration protection during critical range of speed if its vibration value crosses the trip limit ? @CSA

 

Hello Everyone
I have a question regarding critical speed range,
We know when the turbine shaft passes through its critical range of speed its vibration values increases. Will turbine trip on vibration protection during critical range of speed if its vibration value crosses the trip limit ? @CSA

I want to explain it a bit more if its unclear to anyone,
We had a tripping incident during turbine RUN-UP, the vibrations values greatly increased. there is tripping on vibration at 360um with 1s delay, during turbine run-up mode and there is tripping on 240um with 1s delay, during normal turbine running. but it was found during 1st critical speed range(530-730rmp) the bearing vibration increased to 465um and it remained for 10s but turbine did not trip, but after passing through first critical speed turbine tripped on 920rpm at 360um with 1s delay.
so can you please explain with block restrict tripping during start-up in critical range, i could not find such block, i could only see the speed gradient increases during critical range. @WTF?

 

This is a better explanation of what you're looking for, BUT, if there's no block help and nothing in the Operation & Maintenance Manuals about vibration protection when accelerating through critical speeds then GE's attitude is: "You got what you got and you should be happy you got it." Here's the thing about GE turbines, both gas and steam: You may find better but you'll never pay more. And, it's true.

GE doesn't make any money on troubleshooting if they document all of their control and protection schemes. And for $IL protection the technical regulations and standards prohibit them from opening the blocks, even for viewing. If they don't provide any help or documentation, then that's it. Full stop. Period. If you want help, you need to engage the services of GE to help with understanding and troubleshooting. In terms of profit, GE makes far less on the equipment they sell than on selling spare parts and services. FAR less. (The same is true for cars--if you tried to buy a car by buying all the parts necessary to build the car it would cost WAY MORE than the assembled car. And, when you need service, you at least have a choice to take it to the manufacturer's dealer or to a third-party service company/person. And, the automobile companies make a LOT of money on services and parts. And so does GE, and all other manufacturers, by the way--it's NOT just limited to GE. If you buy a Siemens turbine, ONLY Siemens can do ANY work on the turbine. They go so far as to have specialized people who only work on different sections of the turbine so that no one can get enough information about the Siemens turbines to go and start their own service company. And, the T-3000, or whatever it's called today--there are critical components of that PAC (Programmable Action Controller) that ONLY Siemens provides and ONLY Siemens can assist with. So, in some respects, GE isn't the worst, though it could be the best.)

The steam turbine controls group of GE was pretty good about documenting many of the control and protection schemes they were implementing for many decades, but that seems to have gone by the wayside (been abandoned) with digital controls these days. I didn't work too much on steam turbines--primarily because so much of what they did in the application code was undocumented and they just expected people to know how it worked or to deduce it for themselves. Even as a GE employee it was difficult, sometimes impossible, to get answers to technical questions which would have made field engineers and field service people much more productive and worth the money charged for their services and knowledge and skill.

Does the site have a contractual services agreement with GE? If so, can you input this question to them for an answer?

This $IL stuff is crazy, and it just emboldens GE (and other manufacturers) to hide their control schemes behind the technical regulations which were originally put in place to block non-domestic companies from selling their systems by forcing them to spend large sums of money and time developing hardware and software to meet these requirements. It was originally a protectionist scheme which has just gotten out of hand. And is being used by manufacturers to force owners (who spend millions of gazoonies (dollars; euros; yuan; whatever the currency is) to buy this equipment). GE has the attitude their turbines are like modern automobiles--the control systems (computers) are proprietary and with a very few exceptions if you have problems or need service you are forced to go to the dealer for help. Yes; there are OBD and OBD-II readers and codes, but often they're just like GE Diagnostic Alarms--cryptic at best, but mostly gibberish. Without more documention or experience it's impossible to troubleshoot or repair.

And, GE has a new tool to hide behind: Model-Based Control, which is software to predict how a turbine should be operating given current operating conditions (ambient temperature; filter cleanliness; back-pressure; etc.)--and it's ALL hidden and protected from prying eyes. And people pay for this--LOTS of money. And, it requires sensors--lots of additional sensors, many of which are or need to be redundant, and which require time and money to verify calibration and for spares when they fail. (This is primarily for gas turbines, but if it hasn't already been adopted by the steam turbine controls group expect it to be coming soon.)

I wish the news were better. You need to express your unmet needs and requirements to the people who source this equipment and make the purchasing decisions so that in the future they can put in their bid specifications that control and protection schemes FOR THE EQUIPMENT BEING PURCHASED has to be included with the equipment in readable, searchable documents. When enough companies do this, manufacturers are going to wake up and change the way they do business. But, for now, it's too late.

 

Hello Everyone
I have a question regarding critical speed range,
We know when the turbine shaft passes through its critical range of speed its vibration values increases. Will turbine trip on vibration protection during critical range of speed if its vibration value crosses the trip limit ? @CSA

Hi there,
Turbines generally would have trip multiplication when passing through the critical speeds, where the trip values are multiplied by some factors as it is expected that there would be vibrations more than the normal trip levels. I am not sure about how it is with the GE Mark series as I have never worked on them but you may want to check your VMS as it might be doing all the multiplication and trip inhibition etc.

 

I have a question, our wheelspace thermocouple is indicating Out of Range. we have done serious troubleshooting but still not working. We are planning to change the Thermocouple but where the device is located is very tight. My question is
1"What is the normal resistance for good wheelspace thermocouples??
2. How do you know a wheelspace is working very well. .

 

EBUWAODUWA,

This question is TOTALLY UNRELATED to the subject of this thread.

The question of wheelspace thermocouples has been covered MANY TIMES before on Control.com. You can use the Search feature at the top of every Control.com webpage to look for various topics, including this one.

Briefly, the resistance of a good thermocouple is very low. It's extremely difficult for one of two wheelspace thermocouples in a particular wheelspace to be reading a much higher or much lower temperature than the other wheelspace thermocouple--UNLESS IT WAS INSTALLED IMPROPERLY, which has been covered before in several threads on Control.com.

If this problem started after a maintenance outage where the wheelspace thermocouples were removed and then reinstalled (or even new ones were installed after the old ones were removed) it's ENTIRELY possible this particular wheelspace thermocouple was not installed correctly. It's trickly threading them through the guide tubes, and getting them installed in the proper position.

In the future, if you have a question please open a new thread with the question.